Detector module for an X-ray detector

This application claims the benefit of German Patent Application No. DE 10 2023 200 767.3, filed on Jan. 31, 2023, which is hereby incorporated by reference in its entirety.

The present embodiments relate to a detector module for an X-ray detector, to an X-ray detector, and to a computed tomography device including such an X-ray detector.

Independent of the grammatical term usage, individuals with male, female or other gender identities are included within the term.

X-ray detectors are often used for medical imaging examinations of patients. In a computed tomography device (CT device), for example, the X-ray detector and the X-ray source are mounted diametrically opposite each other on a rotor. During the scanning of an object that is to be imaged, the object is positioned in an examination region of the CT device, and the X-ray source and the X-ray detector rotate around the object while the X-ray source emits X-rays. The X-rays traversing the object are detected by one or more detector elements, also referred to as detector pixels or pixel elements, of the X-ray detector, and a measurement signal is generated based on the locally captured X-rays. Because the X-rays interact according to local properties of the object when passing through the object, and, for example, are attenuated, it is possible in this way to make inferences about properties of the object.

In order to suppress the scattered radiation resulting during a scan and potentially leading to a reduction in image quality, X-ray detectors are equipped with anti-scatter collimators, referred to in the following as anti-scatter grids (ASGs). In this case, current-generation CT devices are often equipped with what are referred to as three-dimensional (3D) anti-scatter grids that have an essentially three-dimensional grid structure. These 3D anti-scatter grids enable the scattered radiation to be suppressed in the radial (e.g., φ direction, direction of rotation) and in the axial direction (e.g., feedforward direction, perpendicular to the direction of rotation). Further, in addition to such three-dimensional grid structures, in simpler implementations of anti-scatter grids, it is also possible to use grids of a type that provide collimator walls along one direction only and consequently suppress scattered radiation along the one direction.

An X-ray detector for a CT device typically consists of individual modules that are fixed in place in a carrier unit of the X-ray detector. In this case, the individual module consists of at least one anti-scatter grid and a sensor unit for detecting X-rays. Typically, these functional units are mounted on a carrier (e.g., module carrier) that is included in the detector module and in turn includes means for fixing the module in place in the X-ray detector.

First, it is known in this case to join the anti-scatter grid to the sensor unit by adhesive bonding and to fix the unit in place on the module carrier, which is in turn configured to be securely mounted in the X-ray detector. Second, structures are also known in which both the sensor unit and the anti-scatter grid are connected separately to a module carrier. In this case, the anti-scatter grid then spans the sensor unit in the manner of a bridge.

For example, but not just in the case of a CT device, for achieving optimal image quality, the imaging components are to be aligned and mounted very precisely relative to one another. This consequently applies also to the arrangement of an anti-scatter grid relative to the sensor unit of the X-ray detector or the arrangement of the anti-scatter grid in the X-ray detector itself.

The scope of the present invention is defined solely by the appended claims and is not affected to any degree by the statements within this summary.

The present embodiments may obviate one or more of the drawbacks or limitations in the related art. For example, an improved detector module for an X-ray detector that reduces tolerances occurring between an anti-scatter grid and a sensor unit or a position of the module in the X-ray detector is provided. As another example, an improved X-ray detector and an improved computed tomography device are provided.

The present embodiments relate to a detector module for an X-ray detector including at least one sensor unit for detecting X-rays and at least one anti-scatter grid disposed in a stacking arrangement with the sensor unit. The sensor unit is fixed in place on the anti-scatter grid, and the anti-scatter grid has fastening means (e.g., fasteners) for securely mounting the detector module on a carrier unit of the X-ray detector.

The sensor unit may include a converter unit that is configured to convert incident X-rays into an electrical signal, and a readout unit that is configured to process the electrical signals from the converter unit.

The converter unit may in this case include a direct-converting or an indirect-converting converter material. In direct-converting sensor units, the X-rays or the X-ray photons may be converted into electrical signals by a suitable converter material. Examples for use as converter material include CdTe, CZT, CdZnTeSe, CdTeSe, CdMnTe, InP, TlBr2, HgI2, GaAs, and so forth. In indirect-converting sensor units, the X-rays or the photons may be converted into light by a suitable converter material and into electrical pulses by optically coupled photodiodes (e.g., a photodiode array). Scintillators (e.g., GOS (Gd2O2S), CsJ, YGO or LuTAG) may be employed as the converter material in this case. The converter unit may, for example, have a planar dimension along two directions extending perpendicularly to the stacking direction of the stacking arrangement. The converter unit may be embodied as one piece in a unitary construction or be composed of a plurality of converter elements positioned adjacent to one another along the planar dimension.

A readout unit generally serves for digitizing the electrical signals that are fed in by the converter unit. However, the readout unit may also make provision for more extensive processing operations. A readout unit may be implemented, for example, as an application-specific integrated circuit (ASIC). It is also possible for multiple readout units to be assigned to a unitary or composite sensor unit.

In both types, indirect-converting or direct-converting, the sensor unit may include a plurality of pixel elements (e.g., the smallest planar areas that may be read out independently). In order to be read out, each pixel is connected to an associated evaluation pixel element of a readout unit.

In embodiments, the converter unit is implemented as an indirect-converting converter unit. This may facilitate a fixing of the anti-scatter grid in place directly on the converter unit since the converter material used is often mechanically more robust and less susceptible.

According to the present embodiments, the anti-scatter grid is present in the form of a stacking arrangement with the sensor unit. The stacking direction of the stacking arrangement extends substantially parallel to a radiation incidence direction of X-rays for exposing an X-ray detector when the detector module is used in such a detector.

The anti-scatter grid includes a plurality of collimator walls that are arranged adjacent to one another in at least a first direction perpendicular to a stacking direction. The first direction may then extend, for example, substantially perpendicularly to the radiation incidence direction. The collimator walls are configured or aligned substantially parallel to the stacking direction and are arranged adjacent to one another along the first direction. A deviation of the parallel alignment from the stacking direction of up to 10 degrees (e.g., of less than 5 degrees) may be included. This may include that the collimator walls may be aligned slightly inclined onto a focal point of an X-ray source arranged for the purpose of exposing an X-ray detector by which the anti-scatter grid is encompassed. In this case, the collimator walls are arranged spaced apart relative to one another, such that a thoroughfare channel is provided in each case between two adjacent collimator walls. The alignment substantially along the stacking direction permits the passage of the X-rays from the radiation incidence direction through the anti-scatter grid, whereas X-rays scattered from the radiation incidence direction, which may have a negative impact on the image quality, may be absorbed by the collimator walls.

In addition to the above-described first plurality of collimator walls, the anti-scatter grid may also have a second plurality of collimator walls that are arranged adjacent to one another in a second direction perpendicular to the first direction and perpendicular to the stacking direction. As a result, a 3D anti-scatter grid including a grid-shaped collimator module that enables an improved suppression of the scattered radiation along two directions and thus allows an improvement in image quality to be achieved is provided.

The collimator walls may include a material that absorbs X-rays such that a suppression of scattered radiation that occurs when an object is exposed and irradiated in an imaging application is provided to a sufficient extent, at least along the first direction. The collimator walls include, for example, a material that strongly absorbs X-rays (e.g., has a high absorption coefficient for X-rays; a higher absorption coefficient than bone tissue). For example, the collimator walls may include a metallic material. The collimator walls may include tungsten. However, the plurality of collimator walls may also include lead, molybdenum, zinc, or another material or a composite material.

The fixing of the sensor unit in place on the anti-scatter grid is configured, such way that the connection withstands the forces being exerted during an imaging application. Before the sensor unit is fixed in place, the anti-scatter grid is aligned relative to the sensor unit (e.g., to the pixel elements).

A fixing of the sensor unit in place on the anti-scatter grid may be achieved by an adhesive bonding of the sensor unit to the anti-scatter grid. A permanent connection may be created. In this case, use may be made of an adhesive that does not impede the detection of X-rays in such a way as to have an adverse effect on image quality. The adhesive may include a material having a lower absorption coefficient than the material of the collimator walls. In embodiments, the layer of adhesive for gluing the sensor unit to the anti-scatter grid absorbs less than 5 percent or less than 3%, of a radiant energy that is effective for the imaging. The amount of radiant energy effective for the imaging may denote the radiant energy that would impinge on the detection surface of the detector element, for example, after passing through the anti-scatter grid without adhesive bonding or that would be detected by the detector element. The adhesive may be based, for example, on an epoxy resin, an acrylic resin, or some other potting compound or bonding material.

For example, an adhesive bonding with a scintillator may also be implemented using a reflector adhesive. However, a non-reflecting adhesive may also be used.

The fastening means, which are embodied on the anti-scatter grid, serve for securely mounting the detector module including the stacking arrangement composed of sensor unit and anti-scatter grid to a carrier unit of the X-ray detector. The fastening means may be implemented in different ways provided the fastening means are suitable for achieving a stable mounting of the detector module in the X-ray detector that is also present unchanged when acted upon by the forces exerted during an imaging application (e.g., the centrifugal forces acting on the module during a CT imaging session). In this case, the fastening means may cooperatively interact with corresponding (counter-)fastening means (e.g., counter-fasteners) on the carrier unit of the X-ray detector. The fastening means may be configured, for example, as drilled holes, recesses, or pins. Drilled holes may be configured, for example, such that the drilled holes are suitable for a screw-type connection between carrier unit and detector module. Different fastening means may be embodied on an anti-scatter grid; for example, a drilled hole for a screw-type connection may be embodied on one side of the anti-scatter grid, and a pin may be provided on the other side.

The carrier unit may be configured such that a plurality of detector modules may be fixed in place thereon. The carrier unit may form a frame (e.g., a carrier frame) within which the detector module or detector modules may be arranged and secured. The carrier unit may be, for example, a part of the housing of the X-ray detector.

Since it may be achieved by the fastening means, which are embodied on the anti-scatter grid and serve to secure the module in the X-ray detector, that, in contrast to mounting the detector module including the stacking arrangement composed of sensor unit and anti-scatter grid on a module carrier, via which the mounting in the X-ray detector is achieved, the tolerance resulting when the sensor unit is mounted relative to the carrier is eliminated. This enables the sensor unit to be inserted more accurately in the carrier unit (e.g., in the X-ray detector). Further, compared to a separate mounting of the sensor unit and an anti-scatter grid on a module carrier, the tolerance chain in the case of the relative arrangement via the module carrier is also removed. Further, a cost-effective component may be achieved by dispensing with the module carrier.

In embodiments, the anti-scatter grid may include, for example, a collimator module including the plurality of collimator walls and, on each of two opposite external sides of the collimator module, a retaining element on which the fastening means are embodied. In this case, the external sides are, for example, those sides of the collimator module having planar dimensions that extend parallel to the stacking direction of the stacking arrangement. The retaining elements may be embodied, for example, on those sides on which no sequential arrangement of detector modules is provided in an X-ray detector. When the detector module is used in a CT device, this is, for example, the direction along the axis of rotation (also referred to as the z-axis).

The retaining elements may be configured such that the retaining elements possess an increased mechanical stability in the form of a greater wall thickness owing to the use of a corresponding material or as a result of their geometric design. The retaining elements may be provided, for example, outside of the planar dimension of the sensor unit (e.g., of a converter unit of the sensor unit) in order to avoid the detection of X-rays being compromised. The retaining elements may be present integrally formed with the collimator module in a unitary construction or simply joined thereto, by adhesive bonding, for example. An epoxy glue may be used, for example.

With an adhesive bonding approach, a separate production of the retaining elements and of the collimator module may be provided, with the result, for example, that a more cost-effective method or a less expensive material may be used for the retaining elements than for the collimator module.

Providing a unitary solution enables the anti-scatter grid to be produced in just one manufacturing process, reduces the complexity of the structure, and may provide increased collimator stability.

For example, the anti-scatter grid may be produced by a technique known as rapid manufacturing, also referred to as additive manufacturing technology. Suitable candidates for this include, for example, selective laser melting using radiation-absorbing metallic powder (e.g., tungsten, molybdenum or tantalum).

The retaining elements may, for example, assume a shape that is advantageous for securely mounting the module on the carrier unit and that is coordinated with the carrier unit. For example, the retaining elements may be elongated in one direction or feature a projection relative to the collimator module. The shape of the retaining elements may be matched, for example, to the design of the carrier unit.

Further, the fastening means may be embodied on a side of the anti-scatter grid disposed opposite the sensor unit or on a lateral surface of the anti-scatter grid, the planar dimension of which surface extends parallel to the stacking direction of the stacking arrangement. In contrast to an embodiment on a side of the anti-scatter grid facing toward the sensor unit, for example, the fastening means may be more easily accessible for assembly purposes. A likelihood of damaging the sensor unit during assembly may be reduced.

According to a variant of the detector module, the anti-scatter grid also includes an adjustment means (e.g., an adjustment device) for positioning the anti-scatter grid relative to the carrier unit prior to the anti-scatter grid being fixed in place via the fastening means at least along one direction (e.g., along a direction of rotation or perpendicularly to a direction of rotation of a CT device). The adjustment means may also facilitate a relative positioning along more than one direction. The adjustment means may, for example, cooperatively interact with a corresponding (counter-)adjustment means embodied on the carrier unit. A positioning relative to the carrier unit may be simplified such that a secure mounting via the fastening means is easily made possible and in an aligned position. For example, an adjustment means may be configured as a guide pin or recess. An adjustment relative to the carrier unit would then be possible, for example, using an adjustment means in the form of the guide pin, whereas at the same time, the position of the anti-scatter grid may then be fixed via a screw-type connection using the fastening means in the aligned state. An adjustment means may also be configured, for example, as a stop surface that is provided on the anti-scatter grid and cooperatively interacts with the embodiment of the carrier unit. Other forms of adjustment means may also be provided.

According to an embodiment variant, the anti-scatter grid has at least one stop element for the sensor unit for the purpose of positioning the sensor unit relative to the anti-scatter grid. The sensor unit is then present in the stacking arrangement engaged fully home with the stop element.

An adjustment of the sensor unit relative to the anti-scatter grid may be implemented in a simplified manner. For example, a stop element may be configured in the form of a projection protruding over a radiation exit surface of the collimator module facing toward the sensor unit. The projection forms a stop surface for the sensor unit. The at least one stop element may be embodied, for example, on a collimator wall of the anti-scatter grid in the form of a projection along the stacking direction projecting beyond the wall height of the collimator wall. The stop element is arranged on the anti-scatter grid, for example, such that an area in the stacking arrangement facing toward the sensor unit on the radiation exit side of the anti-scatter grid, which is provided when a stacking arrangement is provided for arranging the sensor element, is limited by the stop element at least on one side by the stop surface of the stop element. For example, a plurality of stop elements that are arranged distributed on the anti-scatter grid such that on at least two sides the plurality of stop elements delimit an area that is equal to the planar dimension of a sensor element that is to be additionally disposed in a stacking arrangement in order to permit an improved alignment along two directions may be provided.

The stop element may be made of the same material as a collimator wall of the anti-scatter grid. The stop element may be present integrally formed in a unitary construction with the collimator wall on which the stop element may be arranged. The stop element may then be fabricated in a joint manufacturing step with the collimator wall on which the stop element is arranged. This may be implemented advantageously by a technique known as rapid manufacturing since, in this case, a high degree of variability in the embodiment of the collimator walls is made possible particularly easily.

According to an embodiment variant, the at least one stop element may also be present as detachable from the anti-scatter grid. For example, the stop element is connected to the anti-scatter grid via a predetermined breaking point in the form of a section having increased porosity or a narrower wall thickness. By a separation of the stop element following a relative positioning, it may be avoided that the stop element obstructs further construction steps.

The present embodiments further relate to an anti-scatter grid having fastening means for use in a detector module according to one of the previously described variants.

The anti-scatter grid may be provided, for example, according to one of the variants of the anti-scatter grid described in connection with the detector module. For example, the anti-scatter grid may be present with retaining elements and/or stop elements. An anti-scatter grid that reduces positioning tolerances occurring when providing a detector module and when installing the detector module in the X-ray detector may be provided.

The present embodiments further relate to an X-ray detector including at least one detector module and a carrier unit for the at least one detector module.

All embodiment variants described in the foregoing with reference to the detector module according to the present embodiments may also be implemented analogously in the X-ray detector. The description provided with regard to the detector module and the previously described advantages may also be applied analogously to the X-ray detector according to the present embodiments.

For example, the X-ray detector may include a plurality of detector modules arranged adjacent to one another, thereby achieving a greater detection area provided by the totality of detector modules.

For example, the carrier unit of the X-ray detector may include (counter-)fastening means (e.g., counter-fasteners) that are embodied in a corresponding manner to the fastening means (e.g., fasteners) of the detector module and cooperatively interact with these for the purpose of securely mounting the detector module. For example, the carrier unit of the X-ray detector may include a (counter-)adjustment means that is configured in a corresponding manner to potential adjustment means (e.g., adjustment device) of the detector module and cooperatively interacts with these for the purpose of positioning the detector module on the carrier unit. For example, the carrier unit may be part of a housing of the X-ray detector.

The present embodiments further relate to a computed tomography device including an X-ray detector according to one of the previously described variants and an X-ray source disposed opposite thereto, which is configured to expose the X-ray detector using X-rays.

For object scanning purposes, an object that is to be imaged may then be placed, for example, between the X-ray source and the detector module or the X-ray detector and irradiated by the X-ray source.

All embodiment variants described hereinabove with reference to the detector module according to the present embodiments and the X-ray detector according to the present embodiments may also be implemented analogously in the computed tomography device. The description provided with regard to the detector module and the X-ray detector and the previously described advantages may also be applied analogously to the computed tomography device according to the present embodiments.

Further, features described in relation to different embodiment variants of the invention may be combined within the scope of the invention to create further embodiment variants of the invention. In addition to the embodiment variants of the invention explicitly described in this application, many other embodiment variants of the invention that the person skilled in the art may realize without leaving the scope of the invention as set forth by means of the claims may be provided.

The use of the indefinite articles “a” or “an” does not exclude the possibility that the feature in question may also be present more than once. The use of the expression “comprise” does not rule out the possibility that the terms linked by the expression “comprise” may be identical. For example, the CT device comprises the CT device. The use of the term “unit” does not rule out the possibility that the object to which the term “unit” refers may include a plurality of components that are separated from one another in space.

shows a detector module in a state mounted on a carrier unit.shows the same detector module as inin an at least partially disassembled view in order to better illustrate the components and the manner of mounting. The following description therefore relates to bothand.